Recording medium feeding device

ABSTRACT

In the device for feeding the recording medium by rotating the roll body by using one feed roller, an angle is formed between the direction of the line segment connecting the centers of rotation of the roll body and the feed roller and the movement direction in which the roll body or the feed roller moves as the diameter of the roll body decreases. For example, in the case where the roll body is moved, the contact point between the roll body and the feed roller shifts to the downstream side of the roll body from the line segment connecting the centers of rotation of the roll body and the feed roller. Therefore, when the roll body is rewound by the feed roller, the contact pressure between the roll body and the feed roller can be increased, and thereby the winding slack of the roll body can be prevented.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording medium feeding device and, more particularly, to a recording medium feeding device for feeding a recording medium by rotating a roll body formed by winding a recording medium in a roll form.

2. Description of the Related Art

As a recording medium feeding device of this type, a device is known in which a roll paper formed by rolling recording paper used as a recording medium is charged in a paper feed unit, and the roll paper is rotated by rotating a feed roller that is in contact with the peripheral surface of the roll paper, by which the roll paper tip end peeled off the roll paper is fed to an image forming location.

FIG. 5 is a view showing the positional relationship between the roll paper and the feed roller in a conventional recording medium feeding device. For convenience, this figure shows a case where a roll paper 1 and a feed roller 2 are arranged perpendicularly.

As shown in FIG. 5, the roll paper 1 and the feed roller 2 are in contact with each other at a contact point 3. By rotating the feed roller 2 in the direction indicated by the arrow in the figure (clockwise direction), the roll paper 1 is rotated in the direction indicated by the arrow a, by which a roll paper tip end 1 a is fed and conveyed.

Although the diameter of the roll paper 1 decreases as paper is consumed, the roll paper 1 can always be brought into contact with the fixed feed roller 2 at the contact point 3 by moving in the direction indicated by the arrow b.

Specifically, support shafts of the roll paper 1 is guided by guide members, not shown, so as to be movable in the direction of a line segment connecting the centers of rotation of the roll paper 1 and the feed roller 2 (the direction indicated by the arrow b). The movement direction of the roll paper 1 is the same as the direction of the above-described line segment, and is perpendicular to a tangential line 4 at the contact point 3 (the paper feed direction) because the contact point 3 also lies on this line segment.

Although the feeding device is provided with one feed roller 2 in the above-described conventional example, some feeding devices are provided with two feed rollers as in other conventional examples (for example, Japanese Patent Application Laid-open No. 10-139239).

In the paper feeding device described in the aforementioned Laid-open, two feed rollers are provided in parallel, and roll paper is placed on these feed rollers. When the roll paper is sent out, the downstream-side feed roller is rotated faster than the upstream-side feed roller. On the other hand, when the roll paper is rewound, the upstream-side feed roller is rotated faster than the downstream-side feed roller, which prevents the paper from slackening.

In the conventional recording medium feeding device having the configuration shown in FIG. 5, in the case where the roll paper tip end 1 a is rewound by rotating the feed roller 2 in the reverse direction (counterclockwise direction) as shown in FIG. 6, the roll paper 1 is subjected to forces in the directions indicated by the arrows c1 and c2 from the feed roller 2 when the feed roller is rotated in the reverse direction, and in particular, the contact pressure at the contact point 3 between the roll paper 1 and the feed roller 2 is lowered by the force in the direction indicated by the arrow c2, which poses a problem in that winding slack occurs. Specifically, if the contact pressure at the contact point 3 lowers, a frictional force between paper on the surface of the roll paper 1 and paper just inside the surface paper decreases, so that the surface paper is much returned by the feed roller 2. As a result, there occurs a phenomenon that the winding of roll paper is slackened. The force in the direction indicated by the arrow c2 is a force in the direction such that the roll paper 1 is movable (retractable) when the roll paper 1 is rotated by the feed roller 2, and acts as a force in the direction such that the load of the feed roller 2 is reduced.

Also, the paper feeding device described in Japanese Patent Application Laid-open No. 10-139239 requires two feed rollers the respective speeds of which can be controlled, which requires extra cost and space. Also, this paper feeding device has a problem in that the occurrence of winding slack caused by the decrease in contact pressure between the roll paper and the feed roller cannot be prevented.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances, and accordingly an object thereof is to provide a recording medium feeding device capable of preventing the winding slack of a recording medium wound on a roll body when the roll body is rewound by one feed roller.

To achieve the above object, a first aspect of the present invention provides a recording medium feeding device in which one of right and left support shafts for holding a roll body formed by winding a recording medium in a roll form and one feed roller for rotating the roll body in such a manner as to be in contact with a peripheral surface of the roll body is fixed, and the other thereof is moved as the diameter of the roll body decreases, wherein an angle is formed between the direction of a line segment connecting the centers of rotation of the roll body and the feed roller and the movement direction in which the roll body or the feed roller moves as the diameter of the roll body decreases, so that when the recording medium is rewound on the roll body by the feed roller, a contact pressure at a contact point between the roll body and the feed roller increases.

That is to say, unlike the conventional example, the relative movement direction between the roll body and the feed roller and the direction of the line segment connecting the centers of rotation of the roll body and the feed roller are not caused to coincide with each other, and an angle is formed. For example, in the case where the feed roller is fixed, and the diameter of the roll body decreases due to the consumption of recording medium and accordingly the roll body is moved, with the movement direction of roll body being a reference, the above-described angle can be formed by arranging the feed roller at a predetermined position (on the downstream side of the roll body from the prolongation of the movement direction of roll body). Inversely, with the arrangement position of feed roller being a reference, the above-described angle can be formed by making the roll body movable in a predetermined direction (direction different from the direction of the line segment connecting the centers of rotation).

Similarly, in the case where the support shafts of the roll body are fixed, and the diameter of the roll body decreases due to the consumption of recording medium and accordingly the feed roller is moved, with the movement direction of feed roller being a reference, the above-described angle can be formed by arranging the support shafts of the roll body at predetermined positions. Also, with the arrangement positions of the support shafts of the roll body being a reference, the above-described angle can be formed by making the feed roller movable in a predetermined direction.

If the above-described angle is formed, a rotational driving force of the feed roller acts so that the contact pressure between the roll body and the feed roller increases when the roll body is rewound by the feed roller, so that the winding slack of the roll body can be prevented.

According to a second aspect of the present invention, in the recording medium feeding device of the first aspect of the present invention, the recording medium feeding device has a pair of right and left guide members for movably guiding the support shafts of the roll body in the radial direction of the roll body and an urging device for urging the roll body to the movement direction of the roll body guided by the guide members, so that the support shaft of the roll body is moved by the guide members and the urging device as the diameter of the roll body decreases, and the feed roller is arranged so that the contact point at which the feed roller is in contact with the roll body shifts from a tangential position at which the movement direction of the roll body moved by being guided by the guide members is a normal to the downstream side of the rotating direction of the roll body.

The contact pressure between the roll body and the feed roller is provided by the gravity of the roll body and an urging force generated by the urging device. When the roller body is rotated in the rewinding direction by the feed roller, a rotational force of the feed roller acts so as to increase the contact pressure, so that the winding slack of the roll body can be prevented.

According to a third aspect of the present invention, in the recording medium feeding device of the second aspect of the present invention, the feed roller is arranged at a position at which taking the maximum radius of the roll body as R1, the minimum radius thereof as R2, and the radius of the feed roller as Rf, an angle θ between a line segment connecting the centers of rotation of the roll body with the maximum radius and the feed roller and a normal corresponding to the movement direction of the roll body is represented by the following inequality. 0<θ<sin⁻¹{(R 2+Rf)/(R 1+Rf)}

The angle θ on the upper limit side in the aforementioned inequality exhibits a condition necessary for the feed roller to be in contact with the roll body even if the roll body comes to have the minimum radius.

According to a fourth aspect of the present invention, in the recording medium feeding device of any one of the first to third aspects of the present invention, the feed roller sends out the recording medium wound on the roll body at the time of normal rotation and rewinds the recording medium on the roll body sent out from the roll body at the time of reverse rotation, and some of a force acting on the roll body from the feed roller at the time of reverse rotation acts in the direction such that the contact pressure between the roll body and the feed roller is increased.

According to a fifth aspect of the present invention, in the recording medium feeding device of any one of the first to fourth aspects of the present invention, the recording medium is a recording paper in which a coloring layer, which is colored by heat and is fixed by light with a predetermined wavelength, is formed on the surface thereof. For the recording paper of this type, if winding slack occurs and the coloring layer is exposed, the image quality is adversely influenced at the subsequent time of image formation. In the present invention, however, since the winding slack is prevented, a cause for adverse influence on the image quality is eliminated, so that high image quality can be obtained.

According to the present invention, in the device for feeding the recording medium by rotating the roll body by using one feed roller, an angle is formed between the direction of the line segment connecting the centers of rotation of the roll body and the feed roller and the movement direction in which the roll body or the feed roller moves as the diameter of the roll body decreases. For example, in the case where the roll body is moved, the contact point between the roll body and the feed roller shifts to the downstream side of the roll body from the line segment connecting the centers of rotation of the roll body and the feed roller. Therefore, when the roll body is rewound by the feed roller, the contact pressure between the roll body and the feed roller can be increased, and thereby the winding slack of the roll body can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the positional relationship between a roll paper and a feed roller, which is used for illustrating the principle of the present invention;

FIG. 2 is a view showing one example of an internal construction of a printer to which a recording medium feeding device in accordance with the present invention is applied;

FIG. 3 is a view showing an embodiment of an internal construction of the feeding device in FIG. 2;

FIG. 4 is a view used for illustrating another embodiment of a recording medium feeding device in accordance with the present invention;

FIG. 5 is a view showing the positional relationship between a roll paper and a feed roller in a conventional recording medium feeding device; and

FIG. 6 is a view used for illustrating a problem arising when a roll paper is rewound in the conventional recording medium feeding device shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a recording medium feeding device in accordance with the present invention will now be described with reference to the accompanying drawings.

First, the principle of the present invention will be described with reference to FIG. 1.

As shown in FIG. 1, a feed roller 12 for rotating a roll paper 10 in the normal or reverse direction is arranged on the downstream side of the roll paper 10 with respect to the position of the conventional feed roller 2 indicated by a broken line (refer to FIGS. 5 and 6).

Although the diameter of the roll paper 10 decreases as recording paper is consumed, the roll paper 10 can always be brought into contact with the fixed feed roller 12 at a contact point 13 by moving in the direction indicated by the arrow b due to the gravity of the roll paper 10 and an urging force applied by an urging device, not shown.

The contact point 13 between the roll paper 10 and the feed roller 12 is shifted to the downstream side in the roll paper feed direction from the prolongation of the movement direction of the roll paper 10. When the recording paper is rewound by rotating the roll paper 10 in the direction indicated by the arrow a by using the feed roller 12, forces applied to the roll paper 10 by the feed roller 12 at the contact point 13 can be represented by the arrows d1 and d2.

The force in the direction indicated by the arrow d1 is a force in the direction connecting the centers of rotation of the roll paper 10 and the feed roller 12, and corresponds to the contact pressure at the contact point 13. The force in the direction indicated by the arrow d2 is a force in the direction of a tangential line 14 at the contact point 13, and corresponds to a rotational driving force transmitted from the feed roller 12 to the roll paper 10.

The force in the direction indicated by the arrow d2 can further be represented by component forces of a force in the direction indicated by the arrow d2 v, which is the same direction as the movement direction of the roll paper 10 (the direction indicated by the arrow b) and a force in the direction indicated by the arrow d2 h, which is perpendicular to the force in the direction indicated by the arrow d2 v. The component force in the direction indicated by the arrow d2 v acts as a force for restraining a force of separation of the roll paper 10 from the feed roller 12.

Thereby, when the roll paper 10 is rewound, the rotational driving force can normally be transmitted from the feed roller 12 to the roll paper 10. In other words, the winding slack of the roll paper 10, which is caused by a phenomenon that the rotational driving force is not transmitted to the roll paper 10 normally and thus the recording paper on the surface of the roll paper 10 is returned much, can be prevented.

Also, in FIG. 1, taking the maximum radius of the roll paper 10 as R1, the minimum radius thereof as R2, and the radius of the feed roller 12 as Rf, an angle θ between a line segment L1 connecting the centers of rotation of the roll paper 10 with the maximum radius and the feed roller 12 and a normal L2 corresponding to the movement direction of the roll paper 10 is represented by the following inequality. 0<θ<sin⁻¹{(R 2+Rf)/(R 1+Rf)}  (1) Wherein, the angle θ on the upper limit side in Inequality (1) exhibits a condition necessary for the feed roller 12 to be in contact with the roll paper 10 even if the roll paper 10 comes to have the minimum radius.

Next, a printer to which the recording medium feeding device in accordance with the present invention is applied will be described.

FIG. 2 is a view showing one example of an internal construction of a printer to which the recording medium feeding device in accordance with the present invention is applied.

As shown in FIG. 2, a printer 100 is a digital color printer of a thermo-autochrome type (hereafter referred to TA type), mainly including a feeding device 20 for the roll paper 10 and an image forming device 50 for forming images on the recording paper fed from the feeding device 20. The details of the feeding device 20 are described later.

The roll paper 10 is a continuous paper formed by winding recording paper 44 on a paper tube 42 so that the image forming surface is directed to the inside. The image forming surface is configured so that, for example, a three coloring layers of cyan (C), magenta (M), and yellow (Y) are formed on a support body, and a heat-resistant protective layer is formed on the uppermost layer.

The image forming device 50 includes a pinch roller 52, a capstan 54, a thermal head 56, a platen roller 58, a cutter portion 60, a Y fixing lamp 62, and an M fixing lamp 64.

The recording paper 44 fed from the feeding device 20 is conveyed at a constant speed by being held between the pinch roller 52 and the capstan 54 in the image forming device 50. When the recording paper 44 is conveyed in the left-to-right direction in FIG. 2 to a predetermined position between the thermal head 56 and the platen roller 58, the thermal head 56 presses on the recording paper 44 to form images on the image forming surface of the recording paper 44.

Specifically, the recording paper 44 is conveyed reciprocatingly three times to form coloring layers of YMC on the image forming surface of the recording paper 44. First, while the recording paper 44 is conveyed, the thermal head 56 is controlled by a Y signal to form a yellow layer on the image forming surface. Subsequently, the yellow color is fixed by the Y fixing lamp 62. Similarly, the thermal head 56 is controlled by an M signal to form a magenta layer on the image forming surface, and the magenta color is fixed by the M fixing lamp 64. Succeedingly, the thermal head 56 is controlled by a C signal, and the cyan layer is formed on the image forming surface. Thereby, color images are printed on the image forming surface of the recording paper 44.

The cutter portion 60 disposed at the rear stage of the thermal head 56 is used to cut the recording paper 44 on which images have been formed into a predetermined size. The recording paper 44 is cut off by being held between upper and lower edges.

Next, the feeding device 20 will be described.

FIG. 3 is a view showing an embodiment of an internal construction of the feeding device 20 of the roll paper 10.

As shown in FIG. 3, the feeding device 20 includes a roll paper case 22 for housing the roll paper 10, the feed roller 12, a guide plate 30 for movably guiding a support shaft 46 attached to the paper tube 42 of the roll paper 10, a pressurizing lever 32 one end of which is turnably attached to the guide plate 30, a coil spring 34 for urging the pressurizing lever 32 in the clockwise direction in FIG. 3, a tip end detector 36 for detecting a roll paper tip end, and a peeling plate 38, which is in contact with the outer peripheral surface of the roll paper 10, for peeling the roll paper tip end from the roll paper 10 to guide a delivery port 37.

The roll paper case 22, being of a substantially cylindrical shape covering the roll paper 10 from upper and lower sides, consists of an upper case 22A serving as a top cover and a lower case 22B. The upper case 22A is opened and closed by a hinge 23.

The guide plate 30 disposed in the roll paper case 22 is formed with a guide groove 30A for guiding the support shaft 46 of the roll paper 10. The roll paper 10 moves along the guide groove 30A when the roll diameter is decreased by the consumption of the recording paper.

The pressurizing lever 32 is in contact with the support shaft 46 of the roll paper 10, and pressurizes the roll paper 10 in the direction such that the roll paper 10 moves downward along the guide groove 30A.

The feed roller 12 is fixedly arranged in the roll paper case 22 so as to be rotatable in the forward and reverse directions, and the outer peripheral surface of the roll paper 10 is always in contact with the feed roller 12 under an appropriate contact pressure. The contact pressure between the roll paper 10 and the feed roller 12 is produced by the gravity of the roll paper 10 and the urging force for urging the roll paper 10 by using the pressurizing lever 32.

As described with reference to FIG. 1, the direction of the line segment connecting the centers of rotation of the roll paper 10 and the feed roller 12 does not coincide with the movement direction of the roll paper 10 (the direction of the guide groove 30A), and the contact point between the roll paper 10 and the feed roller 12 shifts to the downstream side (in the feed direction of the recording paper 44) from the position on the outer peripheral surface at the prolongation of the movement direction of the roll paper 10.

The tip end detector 36 provided in a bottom part of the lower case 22B detects the roll paper tip end by detecting the difference in height of the outer periphery of roll paper 10 when the roll paper 10 is rotated. A detection signal from the tip end detector 36 is used to determine whether or not all of the recording paper 44 has been stored in the roll paper case 22 and the rewinding operation has been finished when the roll paper 10 is rewound, and also to determine whether or not the roll paper tip end has been peeled off the outer peripheral surface of the roll paper 10 by the peeling plate 38 and has been sent out to a delivery port 37.

In the case where the roll paper 10 is rewound by the feed roller 12 as described with reference to FIG. 1, by the arrangement position of the feed roller 12 as configured as described above and the direction of the guide groove 30A in the guide plate 30 (the movement direction of the roll paper 10), some of the rotational driving force of the feed roller 12 acts as a force for pushing the roll paper 10 against the feed roller 12, by which rewinding can be performed without the occurrence of winding slack on the roll paper 10.

The guide groove 30A in the guide plate 30 shown in FIG. 3 is inclined to guide the roll paper 10 movably downward and slantwise to the right. However, the present invention is not limited to this configuration. The guide groove 30A may be arranged so as to guide the roll paper 10 movably in the vertical direction as shown in FIG. 1. In sum, the relative positional relationship between the direction of the guide groove 30A and the arrangement position of the feed roller 12 has only to be kept so that the feed roller 12 lies on the downstream side of the centerline of the guide groove 30A.

Also, in this embodiment, explanation has been given of the configuration in which the feed roller 12 is fixed, and the roll paper 10 is moved by the guide groove 30A in the guide plate 30. However, inversely, the configuration may be such that the roll paper is provided at a fixed position, and the feed roller is moved so as to come into contact with the roll paper under an appropriate contact pressure as the diameter of the roll paper decreases.

Specifically, as shown in FIG. 4, a feed roller 12′ is provided so as to be movable in the direction indicated by the arrow e with respect to the roll paper 10 provided at the fixed position. As shown in the figure, the feeding device is configured so that the contact point between the roll paper 10 and the feed roller 12′ lies on the upstream side of the outer peripheral position of the roll paper 10 at the prolongation of the movement direction e of the feed roller 12′. Thereby, the rotational driving force due to the feed roller 12′ at the time when the roll paper 10 is rewound acts so as to increase the contact pressure of the feed roller 12′, so that the winding slack of the roll paper 10 can be prevented.

Further, in this embodiment, explanation has been given of the roll paper formed by winding the recording paper. However, the invention is not limited to this, but can be applied to a feeding device for a roll body formed by winding a resin sheet, cloth, or any other recording medium. 

1. A recording medium feeding device in which one of right and left support shafts for holding a roll body formed by winding a recording medium in a roll form and one feed roller for rotating the roll body in such a manner as to be in contact with a peripheral surface of the roll body is fixed, and the other thereof is moved as the diameter of the roll body decreases, wherein an angle is formed between the direction of a line segment connecting the centers of rotation of the roll body and the feed roller and the movement direction in which the roll body or the feed roller moves as the diameter of the roll body decreases, so that when the recording medium is rewound on the roll body by the feed roller, a contact pressure at a contact point between the roll body and the feed roller increases.
 2. The recording medium feeding device according to claim 1, wherein the recording medium feeding device has a pair of right and left guide members for movably guiding the support shafts of the roll body in the radial direction of the roll body and an urging device for urging the roll body to the movement direction of the roll body guided by the guide members, so that the support shaft of the roll body is moved by the guide members and the urging device as the diameter of the roll body decreases, and the feed roller is arranged so that the contact point at which the feed roller is in contact with the roll body shifts from a tangential position at which the movement direction of the roll body moved by being guided by the guide members is a normal to the downstream side of the roll body.
 3. The recording medium feeding device according to claim 2, wherein the feed roller is arranged at a position at which taking the maximum radius of the roll body as R1, the minimum radius thereof as R2, and the radius of the feed roller as Rf, an angle θ between a line segment connecting the centers of rotation of the roll body with the maximum radius and the feed roller and a normal corresponding to the movement direction of the roll body is represented by the following inequality. 0<θ<sin⁻¹{(R 2+Rf)/(R 1+Rf)}
 4. The recording medium feeding device according to claim 1, wherein the feed roller sends out the recording medium wound on the roll body at the time of normal rotation and rewinds the recording medium on the roll body sent out from the roll body at the time of reverse rotation, and some of a force acting on the roll body from the feed roller at the time of reverse rotation acts in the direction such that the contact pressure between the roll body and the feed roller is increased.
 5. The recording medium feeding device according to claim 2, wherein the feed roller sends out the recording medium wound on the roll body at the time of normal rotation and rewinds the recording medium on the roll body sent out from the roll body at the time of reverse rotation, and some of a force acting on the roll body from the feed roller at the time of reverse rotation acts in the direction such that the contact pressure between the roll body and the feed roller is increased.
 6. The recording medium feeding device according to claim 3, wherein the feed roller sends out the recording medium wound on the roll body at the time of normal rotation and rewinds the recording medium on the roll body sent out from the roll body at the time of reverse rotation, and some of a force acting on the roll body from the feed roller at the time of reverse rotation acts in the direction such that the contact pressure between the roll body and the feed roller is increased.
 7. The recording medium feeding device according to claim 1, wherein the recording medium is a recording paper in which a coloring layer, which is colored by heat and is fixed by light with a predetermined wavelength, is formed on the surface thereof.
 8. The recording medium feeding device according to claim 2, wherein the recording medium is a recording paper in which a coloring layer, which is colored by heat and is fixed by light with a predetermined wavelength, is formed on the surface thereof.
 9. The recording medium feeding device according to claim 3, wherein the recording medium is a recording paper in which a coloring layer, which is colored by heat and is fixed by light with a predetermined wavelength, is formed on the surface thereof.
 10. The recording medium feeding device according to claim 4, wherein the recording medium is a recording paper in which a coloring layer, which is colored by heat and is fixed by light with a predetermined wavelength, is formed on the surface thereof.
 11. The recording medium feeding device according to claim 5, wherein the recording medium is a recording paper in which a coloring layer, which is colored by heat and is fixed by light with a predetermined wavelength, is formed on the surface thereof.
 12. The recording medium feeding device according to claim 6, wherein the recording medium is a recording paper in which a coloring layer, which is colored by heat and is fixed by light with a predetermined wavelength, is formed on the surface thereof. 